Help!! Will he jump the fence!?!

Ok so I'm training my beagle Jake to jump. I started training him in about June/July, and now his record is 47". My Dad (I'm 14) doesn't really understand the whole dog training thing, and he recons that if I jump Jake over about 30" then it's 'too high'. He has a theory that Jake will one day jump the 57" fence. I know he cannot physically get that high, but parents are stubborn *Sigh*. Fortunatelly I managed to get my father to understand that the DOG CANNOT PHYSICALLY JUMP THE FENCE!!! However... He has now come up with another theory: The dog may see a cat outside the fence one day, and he will somehow jump up 43" and squeeze through the fence were the holes are larger up the top. (About 7" across and 5" high) He has squeezed through the fence as a younger dog, when the fence had no extra wire around the bottom. He saw a cat and went beserk; shoving himself through a hole 10" off the ground. We have since halved the size of these holes. I tried to make Dad see the light by creating exactly the same obstacle, precisely the same size and hight off the ground. As I expected; there was no way on earth he could get through it. Dad still doesn't understand, but I think he realized he was losing the argument when he smashed up ALL my agility equipment and put it out for bulk rubbish. So I've stopped agility.

Can anyone here help my case? I would also like to hear anyone who could help
my fathers side of the case, I don't want to just prove him wrong; I'm trying to find out whether this is possible.